Rundlett K L, Armstrong D W
Department of Chemistry, University of Missouri [Formula: see text] Rolla, Rolla, Missouri 65401.
Anal Chem. 1996 Oct 1;68(19):3493-7. doi: 10.1021/ac960472p.
Micellar-mediated capillary electrophoresis (CE) is used for a wide variety of applications, including the separation of pharmaceuticals, environmental contaminants, illicit drugs, DNA fragments, and many other biological samples. The electrospray ionization interface is one of the most common CE-MS interfaces. Coupling micellar-mediated CE separations with MS detection combines two very powerful, widely applicable analytical techniques. Some types of surfactants strongly interfere with electrospray ionization mass spectrometric (ESI-MS) detection of analytes, and in many cases the ESI-MS analyte signals are completely quenched. Only a few reports have appeared that describe the ESI-MS detection of analytes in the presence of surfactants; however, the exact mechanism of ionization suppression has not yet been addressed. In this work, a modified aerosol ionic redistribution (AIR) model is presented that qualitatively explains the results of previous studies, including those using "polymeric surfactants". Analyte ionization suppression by surfactants appears to be caused by Coulombic interaction between oppositely charged solute and surfactant ions in the ESI-produced offspring droplets. It appears that the ability of surfactants to quench electrospray ionization is directly related to the surface activity and the charge of the surfactant. Also, highly surface active components tend to be enriched in ESI-produced offspring droplets. Analyte ion signals can be detected under conditions that lower the surface concentration of oppositely charged surfactant ions in aerosol droplets. The mechanistic information outlined here may be used to design micellar-mediated CE separations that allow detection of analyte ions by ESI-MS.
胶束介导的毛细管电泳（CE）被广泛应用于多种领域，包括药物、环境污染物、非法药物、DNA片段以及许多其他生物样品的分离。电喷雾电离接口是最常见的CE-MS接口之一。将胶束介导的CE分离与MS检测相结合，融合了两种非常强大且广泛适用的分析技术。某些类型的表面活性剂会强烈干扰分析物的电喷雾电离质谱（ESI-MS）检测，在许多情况下，ESI-MS分析物信号会完全淬灭。仅有少数报告描述了在表面活性剂存在下对分析物的ESI-MS检测；然而，电离抑制的确切机制尚未得到探讨。在这项工作中，提出了一种改进的气溶胶离子重新分布（AIR）模型，该模型定性地解释了先前研究的结果，包括那些使用“聚合表面活性剂”的研究。表面活性剂对分析物电离的抑制似乎是由ESI产生的后代液滴中带相反电荷的溶质和表面活性剂离子之间的库仑相互作用引起的。表面活性剂淬灭电喷雾电离的能力似乎与表面活性剂的表面活性和电荷直接相关。此外，高表面活性成分往往在ESI产生的后代液滴中富集。在降低气溶胶液滴中带相反电荷的表面活性剂离子表面浓度的条件下，可以检测到分析物离子信号。这里概述的机理信息可用于设计胶束介导的CE分离，从而实现通过ESI-MS检测分析物离子。
